Sotaby cutter



A. LATHAM.

ROTARY CUTTER.

APPLICATION FILED mm. 1912.

1,325,645. Patented Dec. 23,1919.-

UNITE mamas ri-rrnr ALBERT LATHAIE, OF BEVERLY, MASSACHUSETTS, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO UNITED SHOE MACHINERY CGBPGRATION, 0F PATERSON NEW JERSEY, A COR- POBATION OF NEW JERSEY.

RQTABY CUTTER.

Application filed April 6, 1917.

edges of the soles, and one of its principal objects is to effect an improvement in the cutter shown in my Patent No. 1,104,910, granted July 28, 1914.

A cutter of this type is mounted for use on the end of a rotary shaft which is driven at a very high speed, usually about 8000 revolutions per minute; and the shoe is guided for the operation of the cutter on the sole edge entirely by the hands of the workman. This-trimming operation gives to the sole edge its final shape and determines the relation of the sole edge to the upper of the shoe. Consequently it determines, to a considerable extent, the style of the shoe. The proper guiding of the shoe for the trimming operation requires great care and skill on the part of the workman since the cutter trims very rapidly and any variation from an accurate guiding of the shoe may cause the cutter to trim into the sole edge too deeply or oven to trim into the upper, in which case the shoe will be rendered unsalable.

The cutter imparts to the sole edge in the trimming operation a transverse contour that is a complement of the transverse contour of the cutter; and for many purposes a cutter is employed that is larger at one end than atthe other so as to give to the edge of the sole a rounded or beveled shape.

Prior to the invention described in my above-mentioned patent it had been the practice to slot these cutters in a direction parallel to the axis of the cutter and in such a manner that the front face of each tooth was parallel to the axis of the cutter, and "formed an acute angle with a radial plane (or plane passing through the axis of the cutter) in other words, this face lay in a elane Specification of Letters Patent.

Patented Dec. 23, 1919.

Serial No. 160,218.

tangent to a cylinder lying within the cutter and coaxial therewith. In using a cutter of this construction it was found that the part of the cutting edge of each tooth at the large end of the cutter began to out before the part of the edge at the small end of the cutter, due to the fact that the part of the cutting edge atthe large end lay in a radial plane angularly in advance of the radial plane containing the part of the cutting edge at the small end of the cutter. The eiiect of this characteristic of the cutter was to crowd the sole toward the small end of the cutter. This crowding action had of course to be counteracted by the workman if he was to trim the sole edge properly, and it greatly increasedthe difiiculty of guiding the shoe accurately for this operation. A further objection to which cutters of this character were open was the fact that the inclined part of the cutting edge oi each tooth had much guiding of the shoe more diiiicult.

These difiiculties were met in my prior invention by slotting the cutter in planes tangent to a cone coaxial with the cutter and having its apex in the direction of the small end of the cutter. The effect of this operation is to swing the angular position of that portion of the cutting edge of each tooth at the large end of the cutter backwardly with relation to the cutting edge at the small end of the cutter by an amount depending upon the slant of the cone upon which the slotting is done, which angle may be made such that the end portions of the cutting edge of each tooth will be brought into the same radial plane. I have found from experience that an angle of 15 degrees would substantially meet this requirement for all styles of shoes' It-will be evident that a cutter, constructed just described, will exert the crowd ing action on the work whichhas been above described in discussing the then existing commercial cutters, since the end portions of the cutting edge of each tooth begin to cut at substantially the same instant and the cutter does not, therefore, tend to crowd the sole in either direction axially of the cutter.

The cutter, as it comes from the milling machine after being slotted, preferably is given a clearance by backing-off. This operation may be performed in a backing-0E machine and by means of a backing-01f tool of the usual construction. Accordin to my former invention, however, the bac ing-ofi tool instead of being fed radially of the cutter as usual, was fed at aslight angle to the radius of the cutter, this angle being such that the main component of the feeding motion was toward the axis of the cutter, while asmaller component was directed parallel to the axis of the cutter and toward the back or larger end of the cutter. The result was to remove the metal from behind the cutting edge of each tooth in a lateral direction as well as in a radial direction, and, consequently, .to skew the contour of the crown of the tooth in addition to backing off the crown. This construction avoids the rubbing and dragging action that, as above stated, is usually exerted on the work by the sharply inclined part of the bed of each tooth.

The angle at which the backing-off operation is performed may be varied as conditions require, but for the more common styles of cutters an angle of about 15 degrees has been found satisfactory. This angle is measured from a radius of the cutter in a radial plane of the cutter. The result just dcscribedmight also be obtained by backing-off the cutter in the usual manner and then giving it a slight 'endwise or axial backing-off, but the first-named method is preferred since it leaves the peripheral face of each tooth of the cutter in such shape that its axial contour will not be changed as it is ground back for the purpose of sharpening. According to the other method, the lip of each tooth would be of uniform thickness from front to back so that a slight change in axial contour would take place as the tooth became thinner from sharpening.

While the construction described, (for a fuller description of which reference may be made to the patent mentioned) was per- :iectly successful in avoiding the difficulties described and came immediately-into great demand in the trade, it was found to be subjectto a diificulty which the present invention designs to overcome. These cutters are mountedin the trimming machine with a guard drawn up against their small ends. It is clear that the lateral backing-off'of the large diametered sharply sloping part of the cutter results in the backing-on of the lip at the small end of the cutter, so that this lip increases in thickness from the front to the back of the tooth. As the cutter wears and is repeatedly ground, while the shape of the cutting edge remains the same (and it is indispensable that it shall remain the same), owing to the backing-off having been done by one continuous movement of the same tool, the relation of the guard to the axial contour varies owing to the continu ally increasing thickness of lip which separates them.

My invention contemplates the obviation of this dilficulty by backing-off the outside face of the lip axially, preferably at substantially the same angle as that used in skewing the contour of the crowns of the teeth. This does away with the increasing thickness of the lip toward the back of the tooth, and in the preferred construction re sults in the formation of a lip of substantially constant thickness along the peripheral face of the tooth and keeps the guard in uniform relation to the cutting edge as the cutter is ground.

This and other features of'the invention will be more clearly understood from the following description of a preferred embodiment thereof, selected for purposes of illustration and shown in the accompanying drawings, in which- Figure 1 shows a front view of the cutter;

Fig. 2 shows an exploded side elevation of the cutter and a guard,

Fig. 3 illustrates the slotting,

Fig. 4 illustrates the backing-off of the cutting part of the tooth,

Fig. 5 illustrates the relations between the guard and the lip in a cutter according to my patent mentioned and according to the present invention,

Fig. 6 illustrates the backing-off of the p,

Fig. 7 shows two positions of the backing off tool of Fig. at, illustrating the clearance formed, and

Fig. 8 is a sectional view of the cutter shown in Fig. 2.

The cutter blank is first turned with a continuous peripheral face and is slotted as shown in Fig. 3. The face 10 of the slotting tool 12 forms the front face let of the tooth. Fig. 3 shows it as entering the cutter blank at the left of the axis 16 and at an angle of aboutl5 to this axis. Fig. 1 illustrates the relation between the front faces of the teeth and the axis of the cutter. It will be noticed that both ends of the same cutting edge lie in the same-radial plane 17, passing through the axis of the cutter.

Fig. 4 illustrates the skewed relation of the crowns of the teeth. The backing-off tool 18 is fed into the work in .a radial plane as the work revolves and at an angle of per- I haps 75 with the axis of the cutter, as

ing-ofi tool 18, toward the large end of the' cutter as the cutting edge of the tooth is departed from. This is well shown inFig. 2

and the left hand view in Fig. 5. Successive positions of the backing-off tool are shown in Fig. 7

The guard 22 fits tightly up against the small end of the cutter, and has a hub 23 which fits into the central bore of the cutter and holds the cutter and guard in alinement. The lip 25 of the guard engages the upper surface of the welt and acts as a guide to hold the work in proper axial relation to the trimming tool.

The change in relation of the guard 22 to the cutting edge as a tooth is ground will be manifest from the left hand view in Fig. 5. The distance from the guard to the base of the lip 24 increases from the dimension shown at 26 to that shown at 28 during the life of the cutter. The formed edge made by the cutter is therefore lowered away from the welt surface, and the appearance of the shoe is changed as the cutter wears down.

This ground of objection to the cutter of my patent I design to obviate by the present invention, which contemplates backing-off the outside face of the lip so that the thickness of the lip will be uniform along the peripheral face of the tooth.

It should be here emphasized that the phenomenon under discussion is not a matter of clearance. If the edge 30 (see Fig. 7) of the backing-01f tool were parallel to the direction of movement of the tool, indicated by the arrow 20 in Figs. a and 7 the edge 30 would cut a conical surface in the cutter,

- having its axis coincident with that of the cutter. This surface would have no clearance. The edge 30 lies, however, along the line 32 making an acute angle with the direction of movement, and will therefore form a clearance as the tool moves into the cutter. This will be apparent from Fig. 7, which illustrates two positions of the cutting edge of the backing-off tool in relation to the axis of the cutter. The first position 36 may be taken as the position of the work itself, and the latter position'35 shows that the first is cleared at every point.

In making cutters embodying this invention I find it advisablefirst to counterbore the cutter as shown at 40, the counterbore being of suflicient diameter to intersect the bottoms of the slots 12. The outside of the lip is then backed-01f by a preferably straight-edged tool 16 which is fed into the cutter on substantially the same angle as that of the arrow 20. This makes the lip wedge-shaped instead of pyramidal and its thickness along the tooth face will be substantially constant. This is shown in Fig. 6 and the right hand View in Fig. 5. One purpose of the counterbore 4:0 is to relieve the edge 17 of the backing off tool of some of-the cutting that it would otherwise be obliged to do. The tool will turn up a heavy bur at the end of its movement unless this counterbore is made. If the counterboring is omitted, the backing off must be carried down as far as the axial opening in the cutter.

The right hand view in Fig. 5 shows how the guard 22 can follow the lip 24 as the tooth face is ground away. The counterbore permits the guard to rest against the forward points of the lips irrespective of the amount of grinding which has been done on the cutter. The lateral relation between the guard and the cutting edge therefore remains unchanged during the life of the cutter.

Having described the invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A rotary cutter having teeth the cutting edges of which have lips and portions having a steep slope relative to the axis of the cutter, the peripheral surfaces of said teeth being backed off laterally toward the portion having the steep slope, and the outer faces of the lips being backed ofl laterally in the same direction.

2. A rotary cutter having teeth with lips and a guard constructed and arranged to rest against said lips the peripheral tooth faces in the neighborhood of said lipsbeing formed by a generatrix moving obliquely to the axis of the cutter, and the outer faces of said lips being formed by a generatrix having substantially the same movement, whereby the relation of said guard to the operating edges of said lips may remain unaltered by the grinding of the cutter.

3. A rotary cutter having teeth with lips, peripheral and lateral faces of the teeth and lips being formed by generatrices having substantially identical movement bearing oblique relation to the axis of the cutter.

1. A rotary cutter having molded cutting teeth the crowns of which are backed off in skewed relation to the axis of the cutter, one end of the cutter having a counterbore intersecting the bases of the teeth, and the ends of the teeth at that end of the cutter being backed off in directions corresponding to the crown-skewing of the respective teeth.

5. A rotary cutter having molded cutting teeth the crowns of which are backed ofi in skewed relation to the axis of the cutter, the axial contour of each of said teeth being uniform throughout the crown and one end, to maintain uniform relation between the crown-contour and a guard seated against the said end of each of the teeth before and after the teeth have been thinned by sharpening them.

6. A rotary cutter having molded cutting teeth the crowns of which are backed 01f in skewed relation to the axis of the cutter, one end of the cutter being backed off as to each tooth in a direction corresponding to that of the crown-skewing to maintain 10 uniform relation between the crowns and the backed-off ends as the teeth are ground for sharpening,

In testimony whereof I have signed my name to this specification.

ALBERT LATHAM. 

